Noise generated by aircraft at the time of takeoff and landing is a large problem for the environment around airports. This noise includes engine noise and aerodynamic noise generated from high-lift devices (such as, slats and flaps), the undercarriage, etc.
Since the high-lift devices, which are one of the sources of the above-mentioned noise, are used to obtain aerodynamic characteristics required at the time of takeoff and landing of the aircraft, they are designed with an emphasis on their aerodynamic characteristics, whereas noise reduction is not taken into consideration.
However, since the noise is a large problem as described above, efforts have been made to reduce the noise of the high-lift devices as well. For example, technologies for achieving a reduction in noise generated at slats serving as the high-lift devices have been proposed (for example, see U.S. Pat. No. 6,394,396.
U.S. Pat. No. 6,394,396 describes a technology in which a balloon that can be inflated and deflated is disposed on a concave part of a slat facing a main wing.
With this technology, when the slat is extended (separated) from the main wing, the balloon is inflated to fill the concave part, thus suppressing the occurrence of aerodynamic noise due to turbulence caused by the concave part.
The concave part is provided to ensure space for avoiding interference with the leading edge of the main wing when the slat is retracted into (is brought into contact with) the main wing.